Process for forming a vessel

ABSTRACT

A vessel and method for forming the vessel is disclosed, the vessel having a hollow liner, at least one boss, and a filament wound outer shell, wherein at least a portion of the hollow liner if formed by at least one of an co-extrusion blow film molding process, a thermoplastic foiling process, and a coating process.

FIELD OF THE INVENTION

The invention relates to a vessel and more particularly to a pressurevessel and a method for forming the vessel, wherein the vessel includesa hollow liner formed from an extruded film tube and a pair of end caps.

BACKGROUND OF THE INVENTION

Presently, there are a variety of vessels designed to contain variousfluids such as compressed natural gas (CNG), hydrogen gas for use in afuel cell, and the like, for example. A common technique for storing thefluid is in a lightweight, high pressure vessel resistant to punctures.Traditionally, such vessels are divided into four types. A Type I vesselis a metal vessel. A Type II vessel is also a metal vessel, the vesselhaving an outer composite shell disposed on a cylindrical sectionthereof. A Type III vessel consists of a liner produced from a metalsuch as steel and aluminum, for example, and an outer composite shellthat encompasses the liner and militates against damage thereto. A TypeIV vessel is substantially similar to the Type III vessel, wherein theliner is produced from a plastic.

Typically, the liner is manufactured using conventional formingprocesses such as a welding process, a rotational molding process, andother similar processes, for example. During the welding process,multiple components of the liner are welded together at seams of thecomponents. The weld seams, however, may not be fluid-tight and permitpermeation of the stored fluid from the vessel. Further, the weldingprocess limits the types of material which can be used to form theliner. On the other hand, the rotational molding process is slower andproduces a liner having an adverse thickness. During the rotationalmolding process, the liner is formed by disposing bosses in a die cavitywith a polymer resin, heating the mold while being rotated to cause theresin to melt and coat walls of the die cavity, cooling the die, andremoving the molded liner. The bosses, however, may not properly adhereto the liner resulting in formation of a space therebetween. If thebosses are not properly adhered to the liner, a fluid-tight seal betweenthe bosses and the liner may not form. Without a fluid-tight seal, thecontents of the vessel may escape therefrom to the atmosphere. To ensurefluid-tight seals between the bosses and the liner, adhesives, heatwelding, and other similar processes may be employed. Alternatively, anadapter device as disclosed in U.S. Pat. No. 7,032,767, herebyincorporated herein by reference in its entirety, may also be used toensure a fluid-tight seal. Such processes and additional devices may betime consuming and require manual process steps, thereby resulting in anincreased cost to produce the vessel.

It would be desirable to develop a vessel and a method for producing thevessel including a thin hollow liner and at least one boss, wherein anefficiency of the method is optimized and a cost thereof is minimized.

SUMMARY OF THE INVENTION

In accordance and congruent with the present invention, a vessel and amethod for producing the vessel including a hollow liner and at leastone boss, wherein an efficiency of the method is optimized and a costthereof is minimized, has surprisingly been discovered.

In one embodiment, a method of forming a vessel, the method comprisesthe steps of: forming a hollow liner including a first end cap and asecond end cap, wherein the first end cap includes a first boss and thesecond end cap includes a second boss; and forming an outer shell overat least a portion of the hollow liner and at least a portion of thebosses.

In another embodiment, a method of forming a vessel, the methodcomprises the steps of: forming a first end cap of a hollow linerincluding an interfacial layer and a first boss; forming a main body ofthe hollow liner; disposing the first end cap on the main body of thehollow liner; and forming an outer shell over the main body and at leasta portion of the first end cap of the hollow liner.

In another embodiment, a vessel comprises: a first end cap including aninterfacial layer and a first boss; a thin main body abutting at least aportion of the first end cap; and an outer shell formed around at leasta portion of the first end cap and the main body.

DESCRIPTION OF THE DRAWINGS

The above, as well as other advantages of the present invention, willbecome readily apparent to those skilled in the art from the followingdetailed description of a preferred embodiment when considered in thelight of the accompanying drawings in which:

FIG. 1 is a cross-sectional elevational view of a vessel according to anembodiment of the invention;

FIG. 2 is a cross-sectional elevational view of a vessel according toanother embodiment of the invention; and

FIG. 3 is a cross-sectional elevational view of a vessel according toanother embodiment of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT

The following detailed description and appended drawings describe andillustrate various exemplary embodiments of the invention. Thedescription and drawings serve to enable one skilled in the art to makeand use the invention, and are not intended to limit the scope of theinvention in any manner. In respect of the methods disclosed, the stepspresented are exemplary in nature, and thus, the order of the steps isnot necessary or critical.

FIG. 1 illustrates a vessel 10. The vessel 10 includes a hollow liner 12having a thin main body 13, a first end cap 14, and a second end cap 15.In the embodiment shown, the vessel 10 further includes an outer shell16. The vessel 10 has a substantially cylindrical shape and is adaptedto hold a pressurized fluid (not shown). It is understood that thevessel 10 may have any shape as desired, and the vessel 10 may includeadditional layers such as a barrier layer, a foil layer, a porouspermeation layer, and the like, as desired. The pressurized fluid may beany fluid such as a gas (e.g. hydrogen gas and oxygen gas), a liquid,and both a liquid and a gas, for example. As shown, the main body 13 ofthe liner 12 is formed from a moldable material such as polyethylene,polypropylene, polyethylene terephthalate (PET), ethylene vinyl alcohol,and a polyamide, for example. The main body 13 is formed from a thinfilm having a desired thickness. In a non-limiting example, the mainbody 13 is about 0.1 mm to about 0.5 mm thick.

The first end cap 14 of the liner 12 includes an interfacial layer 17and a first divided boss 20. As shown, the interfacial layer 17 of thefirst end cap 14 is formed from a moldable material such aspolyethylene, PET, polyoxymethylene (POM), ethylene vinyl alcohol, and apolyamide, for example. A first component 21 of the first divided boss20 substantially abuts at least a portion of a first surface of theinterfacial layer 17. A first gasket 22 such as a polymeric o-ring, forexample, is disposed between the first component 21 and the interfaciallayer 17 to form a substantially fluid-tight seal therebetween. It isunderstood that the first gasket 22 may be disposed elsewhere betweenthe first component 21 and the interfacial layer 17 of the liner 12, ifdesired.

A second component 24 of the first divided boss 20 substantially abutsat least a portion of a second surface of the interfacial layer 17. Thesecond component 24 cooperates with the first component 21 to secure theinterfacial layer 17 therebetween. A second gasket 26 such as apolymeric o-ring, for example, is disposed between the first component21 and the second component 24 of the first divided boss 20 to form asubstantially fluid-tight seal therebetween. The second component 24receives a fluid-communication element (not shown) in a central apertureformed therein for communicating with an interior 27 of the vessel 10such as a valve, a fitting, a hose, a nozzle, a conduit, and the like,for example. It is understood that the second gasket 26 may be disposedelsewhere between the first component 21 and the second component 24, ifdesired. The gaskets 22, 26 may be any conventional gasket formed from amaterial which facilitates forming a fluid-tight seal between twocontacting surfaces. The first component 21 and the second component 24of the first divided boss 20 are separately produced finishes that forman opening into the interior 27 of the vessel 10, and are typicallyshaped to receive a closure element (not shown). The vessel 10 mayinclude any number of divided bosses, as desired. The components 21, 24of the first divided boss 20 may be formed from any suitable materialhaving desired properties such as a metal, for example.

The second end cap 15 of the liner 12 includes an interfacial layer 29and a second divided boss 30. As shown, the interfacial layer 29 of thesecond end cap 15 is formed from a moldable material such aspolyethylene, PET, POM, ethylene vinyl alcohol, and a polyamide, forexample. A first component 32 of the second divided boss 30substantially abuts at least a portion of a first surface of theinterfacial layer 29. A third gasket 34 such as a polymeric o-ring, forexample, is disposed between the first component 32 and the interfaciallayer 29 to form a substantially fluid-tight seal therebetween. It isunderstood that the third gasket 34 may be disposed elsewhere betweenthe first component 32 and the interfacial layer 29, if desired.

A second component 36 of the second divided boss 30 substantially abutsat least a portion of a second surface of the interfacial layer 29. Thesecond component 36 cooperates with the first component 32 to secure theinterfacial layer 29 therebetween. A fourth gasket 38 such as apolymeric o-ring, for example, is disposed between the first component32 and the second component 36 of the second divided boss 30 to form asubstantially fluid-tight seal therebetween. The second component 36receives a fluid-communication element (not shown) in a central apertureformed therein for communicating with an interior 27 of the vessel 10such as a valve, a fitting, a hose, a nozzle, a conduit, and the like,for example. It is understood that the fourth gasket 38 may be disposedelsewhere between the first component 32 and the second component 36, ifdesired. The gaskets 34, 38 may be any conventional gasket formed from amaterial which facilitates forming a fluid-tight seal between twocontacting surfaces. The first component 32 and the second component 36of the second divided boss 30 are separately produced finishes that forman opening into the interior 27 of the vessel 10, and are typicallyshaped to receive a closure element (not shown). The vessel 10 mayinclude any number of divided bosses, as desired. The components 32, 36of the second divided boss 30 may be formed of a metal or anotherconventional material having desired properties.

In the embodiment shown, the outer shell 16 of the vessel 10substantially abuts at least a portion of the second surface of theliner 12. A portion of the outer shell 16 is disposed on the secondcomponent 24 of the first divided boss 20 and the second component 36 ofthe second divided boss 30. The outer shell 16 is typically formed by afilament winding and curing process. When the outer shell 16 is formedby the filament winding and curing process, the outer shell 16 may beformed from a carbon fiber, a glass fiber, a composite fiber, and afiber having a resin coating, for example. It is understood that theouter shell 16 can be formed by other methods as desired.

To form the vessel 10, the thin main body 13 of the liner 12 is formedby a co-extrusion blow film molding process. After the main body 13 ofthe liner 12 has been formed, the first end cap 14 and the second endcap 15 of the liner 12 are disposed on opposing ends thereof. The firstend cap 14 and the second end cap 15 are formed by any conventionalforming process such as an injection molding process, a thermoformingprocess, and the like, for example. The outer shell 16 is then formedaround the main body 13 and at least a portion of the end caps 14, 15using the filament winding and curing process. Once the outer shell 16is cured, the vessel 10 is complete.

Alternatively, the liner 12 is formed by a thermoplastic foiling andsealing process. During the thermoplastic foiling and sealing process, athin foil sheet is formed by a thermoplastic foiling process. It isunderstood that the thin foil sheet can be a single layer, flexible,foil sheet or a multi-layer, flexible, foil sheet as desired. It isfurther understood that an additional coating process may be employed toapply to the thin foil sheet a material to militate against a permeationof the pressurized fluid therethrough such as a hydrogen barriermaterial, for example. The end caps 14, 15 are then disposed on opposingends of the thin foil sheet. The thin foil sheet is wound around thefirst end cap 14 and the second end cap 15. A seem formed at contactingedges of the foil sheet is then sealed to form the main body 13.Thereafter, seems formed at contacting surfaces of the main body 13 andthe respective end caps 14, 15 are sealed to form the liner 12. It isunderstood that the seems can be sealed by any suitable method asdesired such as by a welding process, a heat-sealing process, and thelike, for example. The first end cap 14 and the second end cap 15 areformed by any conventional forming process such as an injection moldingprocess, a thermoforming process, and the like, for example.

FIG. 2 shows a vessel 10′ according to another embodiment of theinvention. The embodiment of FIG. 2 is similar to the vessel 10 of FIG.1, except as described hereinafter. Similar to the structure of FIG. 1,FIG. 2 includes the same reference numerals accompanied by a prime (′)to denote similar structure.

The vessel 10′ includes a hollow liner 12′ having a thin main body 13′,a first end cap 14′, and a second end cap 15′. In the embodiment shown,the vessel 10′ further includes an outer shell 16′. The vessel 10′ has asubstantially cylindrical shape and is adapted to hold a pressurizedfluid (not shown). It is understood that the vessel 10′ may have anyshape as desired, and the vessel 10′ may include additional layers suchas a barrier layer, a foil layer, a porous permeation layer, and thelike, as desired. The pressurized fluid may be any fluid such as a gas(e.g. hydrogen gas and oxygen gas), a liquid, and both a liquid and agas, for example. As shown, the main body 13′ of the liner 12′ is formedfrom a moldable material such as polyethylene, PET, ethylene vinylalcohol, and a polyamide, for example. The main body 13′ is formed froma thin film having a desired thickness. In a non-limiting example, themain body 13′ is about 0.1 mm to about 0.5 mm thick.

The first end cap 14′ of the liner 12′ includes an interfacial layer 17′and a boss 120. The interfacial layer 17′ is formed around at least aportion of the boss 120. As shown, the interfacial layer 17′ is formedfrom a moldable material such as a thermoplastic (e.g. polycarbonate,polyethylene, PET, POM, ethylene vinyl alcohol, a polyamide, and afiberglass thermoplastic), for example. The boss 120 receives afluid-communication element (not shown) in a central aperture formedtherein for communicating with an interior 27′ of the vessel 10′ such asa valve, a fitting, a hose, a nozzle, a conduit, and the like, forexample. A first gasket 122 such as a polymeric O-ring, for example, maybe disposed adjacent an annular shoulder 124 of the interfacial layer17′ and an inner surface 126 of the boss 120. The gasket 122 is adaptedto form a fluid-tight seal between the interfacial layer 17′ and thefluid-communication element. It is understood that the gasket 122 may bedisposed elsewhere between the interfacial layer 17′ and thefluid-communication element, if desired. The gasket 122 may be anyconventional gasket formed from a material which facilitates forming afluid-tight seal between two contacting surfaces. The boss 120 istypically a separately produced finish that forms an opening into theinterior 27′ of the vessel 10′, and is shaped to receive a closureelement (not shown). The vessel 10′ may include any number of bosses, asdesired. The boss 120 may be formed from any suitable material havingdesired properties such as a metal, for example.

The second end cap 15′ of the liner 12′ includes an interfacial layer29′ and a boss 130. The interfacial layer 29′ is formed around at leasta portion of the boss 130. As shown, the interfacial layer 29′ is formedfrom a moldable material such as a thermoplastic (e.g. polycarbonate,polyethylene, PET, POM, ethylene vinyl alcohol, a polyamide, and afiberglass thermoplastic), for example. The boss 130 receives afluid-communication element (not shown) in a central aperture formedtherein for communicating with the interior 27′ of the vessel 10′ suchas a valve, a fitting, a hose, a nozzle, a conduit, and the like, forexample. A second gasket 132 such as a polymeric o-ring, for example,may be disposed adjacent an annular shoulder 134 of the interfaciallayer 29′ and an inner surface 136 of the boss 130. The gasket 132 isadapted to form a fluid-tight seal between the interfacial layer 29′ andthe fluid-communication element. It is understood that the gasket 132may be disposed elsewhere between the interfacial layer 29′ and thefluid-communication element, if desired. The gasket 132 may be anyconventional gasket formed from a material which facilitates forming afluid-tight seal between two contacting surfaces. The boss 130 istypically a separately produced finish that forms an opening into theinterior 27′ of the vessel 10′, and is shaped to receive a closureelement (not shown). The vessel 10′ may include any number of bosses, asdesired. The boss 130 may be formed from any suitable material havingdesired properties such as a metal, for example.

In the embodiment shown, the outer shell 16′ of the vessel 10′substantially abuts at least a portion of the liner 12′. A portion ofthe outer shell 16′ is disposed on the boss 120 and the boss 130. Theouter shell 16′ is typically formed by a filament winding and curingprocess. When the outer shell 16′ is formed by the filament winding andcuring process, the outer shell 16′ may be formed from a carbon fiber, aglass fiber, a composite fiber, and a fiber having a resin coating, forexample. It is understood that the outer shell 16′ can be formed byother methods as desired.

To form the vessel 10′, the thin main body 13′ of the liner 12′ isformed by a co-extrusion blow film molding process. After the main body13′ of the liner 12′ has been formed, the first end cap 14′ and thesecond end cap 15′ of the liner 12′ are disposed on opposing endsthereof. The first end cap 14′ and the second end cap 15′ are formed byany conventional forming process such as an injection molding process, athermoforming process, and the like, for example. The outer shell 16′ isthen formed around the main body 13′ and at least a portion of the endcaps 14′, 15′ using the filament winding and curing process. Once theouter shell 16′ is cured, the vessel 10′ is complete.

Alternatively, the liner 12′ is formed by a thermoplastic foiling andsealing process. During the thermoplastic foiling and sealing process, athin foil sheet is formed by a thermoplastic foiling process. It isunderstood that the thin foil sheet can be a single layer, flexible,foil sheet or a multi-layer, flexible, foil sheet as desired. It isfurther understood that an additional coating process may be employed toapply to the thin foil sheet a material to militate against a permeationof the pressurized fluid therethrough such as a hydrogen barriermaterial, for example. The end caps 14′, 15′ are then disposed onopposing ends of the thin foil sheet. The thin foil sheet is woundaround the first end cap 14′ and the second end cap 15′. A seem formedat contacting edges of the foil sheet is then sealed to form the mainbody 13′. Thereafter, seems formed at contacting surfaces of the mainbody 13′ and the respective end caps 14′, 15′ are sealed to form theliner 12′. It is understood that the seems can be sealed by any suitablemethod as desired such as by a welding process, a heat-sealing process,and the like, for example. The first end cap 14′ and the second end cap15′ are formed by any conventional forming process such as an injectionmolding process, a thermoforming process, and the like, for example.

FIG. 3 shows a vessel 10″ according to another embodiment of theinvention. The embodiment of FIG. 3 is similar to the vessel 10, 10′ ofFIGS. 1 and 2, except as described hereinafter. Similar to the structureof FIGS. 1 and 2, FIG. 3 includes the same reference numeralsaccompanied by a prime (″) to denote similar structure.

The vessel 10″ includes a hollow liner 12″ having a thin main body 13″,a first end cap 14″, and a second end cap 15″. In the embodiment shown,the vessel 10″ further includes an outer shell 16″. The vessel 10″ has asubstantially cylindrical shape and is adapted to hold a pressurizedfluid (not shown). It is understood that the vessel 10″ may have anyshape as desired, and the vessel 10″ may include additional layers suchas a barrier layer, a foil layer, a porous permeation layer, and thelike, as desired. The pressurized fluid may be any fluid such as a gas(e.g. hydrogen gas and oxygen gas), a liquid, and both a liquid and agas, for example. As shown, the main body 13″ of the liner 12″ is formedfrom a moldable material such as polyethylene, PET, ethylene vinylalcohol, and a polyamide, for example. The main body 13″ is formed froma thin film having a desired thickness. In a non-limiting example, themain body 13″ is about 0.1 mm to about 0.5 mm thick.

The first end cap 14″ of the liner 12″ includes an interfacial layer 17″and a boss 220. As shown, the interfacial layer 17″ and the boss 220 areintegrally formed. It is understood that the boss 220 may be formed froma reinforced material if desired. The boss 220 receives afluid-communication element (not shown) in a central aperture formedtherein for communicating with an interior 27″ of the vessel 10″ such asa valve, a fitting, a hose, a nozzle, a conduit, and the like, forexample. A first gasket 122″ such as a polymeric o-ring, for example,may be disposed adjacent an annular shoulder 224 and an inner surface126″ of the boss 220. The gasket 122″ is adapted to form a fluid-tightseal between the boss 220 and the fluid-communication element. It isunderstood that the gasket 122″ may be disposed elsewhere between theboss 220 and the fluid-communication element, if desired. The gasket122″ may be any conventional gasket formed from a material whichfacilitates forming a fluid-tight seal between two contacting surfaces.The vessel 10″ may include any number of bosses, as desired. The end cap14″ may be formed from any suitable material having desired propertiessuch as a metal, for example.

The second end cap 15″ of the liner 12″ includes an interfacial layer29″ and a boss 230. As shown, the interfacial layer 29″ and the boss 230are integrally formed. It is understood that the boss 230 may be formedfrom a reinforced material if desired. The boss 230 receives afluid-communication element (not shown) in a central aperture formedtherein for communicating with the interior 27″ of the vessel 10″ suchas a valve, a fitting, a hose, a nozzle, a conduit, and the like, forexample. A second gasket 132″ such as a polymeric o-ring, for example,may be disposed adjacent an annular shoulder 234 and an inner surface136″ of the boss 230. The gasket 132″ is adapted to form a fluid-tightseal between the boss 230 and the fluid-communication element. It isunderstood that the gasket 132″ may be disposed elsewhere between theboss 230 and the fluid-communication element, if desired. The gasket132″ may be any conventional gasket formed from a material whichfacilitates forming a fluid-tight seal between two contacting surfaces.The vessel 10″ may include any number of bosses, as desired. The end cap15″ may be formed from any suitable material having desired propertiessuch as a metal, for example.

In the embodiment shown, the outer shell 16″ of the vessel 10″substantially abuts at least a portion of the liner 12″. A portion ofthe outer shell 16″ is disposed on the bosses 220, 230 of the respectiveend caps 14″, 15″. The outer shell 16″ is typically formed by a filamentwinding and curing process. When the outer shell 16″ is formed by thefilament winding and curing process, the outer shell 16″ may be formedfrom a carbon fiber, a glass fiber, a composite fiber, and a fiberhaving a resin coating, for example. It is understood that the outershell 16″ can be formed by other methods as desired.

To form the vessel 10″, the thin main body 13″ of the liner 12″ isformed by a co-extrusion blow film molding process. After the main body13″ of the liner 12″ has been formed, the first end cap 14″ and thesecond end cap 15″ of the liner 12″ are disposed on opposing endsthereof. The first end cap 14″ and the second end cap 15″ are formed byany conventional forming process such as a casting process, for example.The outer shell 16″ is then formed around the main body 13″ and at leasta portion of the end caps 14″, 15″ using the filament winding and curingprocess. Once the outer shell 16″ is cured, the vessel 10″ is complete.

Alternatively, the liner 12″ is formed by a thermoplastic foiling andsealing process. During the thermoplastic foiling and sealing process, athin foil sheet is formed by a thermoplastic foiling process. It isunderstood that the thin foil sheet can be a single layer, flexible,foil sheet or a multi-layer, flexible, foil sheet as desired. It isfurther understood that an additional coating process may be employed toapply to the thin foil sheet a material to militate against a permeationof the pressurized fluid therethrough such as a hydrogen barriermaterial, for example. The end caps 14″, 15″ are then disposed onopposing ends of the thin foil sheet. The thin foil sheet is woundaround the first end cap 14″ and the second end cap 15″. A seem formedat contacting edges of the foil sheet is then sealed to form the mainbody 13″. Thereafter, seems formed at contacting surfaces of the mainbody 13″ and the respective end caps 14″, 15″ are sealed to form theliner 12″. It is understood that the seems can be sealed by any suitablemethod as desired such as by a welding process, a heat-sealing process,and the like, for example. The first end cap 14″ and the second end cap15″ are formed by any conventional forming process such as a castingprocess, for example.

From the foregoing description, one ordinarily skilled in the art caneasily ascertain the essential characteristics of this invention and,without departing from the spirit and scope thereof, can make variouschanges and modifications to the invention to adapt it to various usagesand conditions.

What is claimed is:
 1. A method of forming a vessel, the methodcomprising the steps of: forming a first end cap of a hollow liner, thefirst end cap including an interfacial layer and a first boss, theinterfacial layer defined by an inner surface and a second surfaceopposing the inner surface, and terminating in an end surface; forming amain body of the hollow liner in a step separate from the forming of thefirst end cap of the hollow liner, the main body having an inner surfaceand a first end of the main body terminating in an end surface;disposing the first end cap on the main body of the hollow liner,wherein the end surface of the interfacial layer abuts the end surfaceof the main body to define an interface between the first end cap andthe main body of the hollow liner; and forming an outer shell over themain body, the interface, at least a portion of the first boss, and atleast a portion of the first end cap of the hollow liner to secure themain body to the first end cap, wherein the inner surface of theinterfacial layer and the inner surface of the main body together definean interior cavity of the vessel for containing a pressurized fluid,wherein the inner surface of the main body is a major surface of theinterior cavity and the inner surface of the interfacial layer is aminor surface of the interior cavity, wherein at least a first portionof the first boss is disposed between the outer shell and the secondsurface of the interfacial layer in an axial direction of the first bossand a second portion of the first boss is disposed adjacent the innersurface of the interfacial layer, wherein the interfacial layer is indirect contact with the first portion of the first boss and the secondportion of the first boss, and wherein the outer shell is in directcontact with an outer surface of the first boss and the interfaciallayer.
 2. The method according to claim 1, wherein the interfacial layerof the first end cap cooperates with the first boss to form asubstantially fluid-tight seal therebetween.
 3. The method according toclaim 1, wherein the interfacial layer of the first end cap and thefirst boss are integrally formed.
 4. The method according to claim 1,wherein the first end cap is formed by one of an injection moldingprocess and a thermoforming process.
 5. The method according to claim 1,wherein the main body is formed by at least one of a co-extrusion blowfilm molding process, a thermoplastic foiling process, and a coatingprocess.
 6. The method according to claim 1, wherein the outer shell isformed by a filament winding and curing process.
 7. The method accordingto claim 1, further comprising the steps of forming a second end cap ofthe hollow liner, the second end cap including an interfacial layer anda second boss; disposing the second end cap on the main body of thehollow liner; and forming the outer shell over at least a portion of thesecond end cap of the hollow liner.
 8. The method according to claim 7,wherein the interfacial layer of the second end cap cooperates with thesecond boss to form a substantially fluid-tight seal therebetween. 9.The method according to claim 7, wherein the interfacial layer of thesecond end cap and the second boss are integrally formed.
 10. The methodaccording to claim 7, wherein the second end cap is formed by one of aninjection molding process and a thermoforming process.
 11. A vesselcomprising: a first end cap including an interfacial layer and a firstboss, the interfacial layer defined by an inner surface and a secondsurface opposing the inner surface, and terminating in an end surface,the first boss having a first component and a second component, whereinthe second component abuts an inner surface of the first component andan outer surface of the first component; a thin main body having aninner surface and a first end terminating in an end surface, the endsurface at the first end of the main body abutting the end surface ofthe interfacial layer of the first end cap to define an interfacebetween the first end cap and the main body; and an outer shell formedaround at least a portion of the first end cap, the interface, at leasta portion of the first boss, and the main body and securing the mainbody to the first end cap with at least a portion of the first bossdisposed between the outer shell and second surface of the interfaciallayer in an axial direction of the first boss, wherein the inner surfaceof the interfacial layer and the inner surface of the main body togetherdefine an interior cavity of the vessel for containing a pressurizedfluid, wherein the inner surface of the main body is a major surface ofthe interior cavity and the inner surface of the interfacial layer is aminor surface of the interior cavity, and wherein the outer shell is indirect contact with an outer surface of the first boss and theinterfacial layer.
 12. The vessel according to claim 11, furthercomprising a second end cap including an interfacial layer and a secondboss.
 13. The vessel according to claim 12, wherein at least one of theinterfacial layer of the first end cap and the first boss are integrallyformed and the interfacial layer of the second end cap and the secondboss are integrally formed.
 14. The vessel according to claim 12,wherein at least one of the first end cap and the second end cap isformed by one of an injection molding process and a thermoformingprocess.
 15. The vessel according to claim 11, wherein the main body isformed by at least one of a co-extrusion blow film molding process, athermoplastic foiling process, and a coating process.
 16. A method offorming a vessel comprising: disposing a first end cap on a first end ofa main body, the first end cap and the main body formed in separatesteps, the first end of the main body having an inner surface and asecond surface opposing the inner surface, and terminating in an endsurface, wherein the first end cap includes a first boss and aninterfacial layer having an inner surface and terminating in an endsurface, the end surface at the first end of the main body abutting theend surface of the interfacial layer of the first end cap to define afirst interface between the first end cap and the main body, wherein thefirst boss has a first component, a second component, and a firstgasket, the first component of the first boss cooperating with thesecond component of the first boss to secure the interfacial layer ofthe first end cap therebetween, and the first gasket of the first bossdisposed between the first component of the first boss and theinterfacial layer of the first end cap in an axial direction of thefirst boss to form a substantially fluid tight seal therebetween;disposing a second end cap on a second end of the main body, the secondend cap and the main body formed in separate steps, the second enddisposed opposite the first end of the main body, the second end of themain body having an inner surface and terminating in an end surface,wherein the second end cap includes a second boss and an interfaciallayer terminating in an end surface, the end surface at the second endof the main body abutting the end surface of the interfacial layer ofthe second end cap to define a second interface between the first endcap and the main body, wherein the second boss has a first component, asecond component, and a first gasket the first component of the secondboss cooperating with the second component of the second boss to securethe interfacial layer of the second end cap therebetween and the firstgasket of the second boss disposed between the first component of thesecond boss and the interfacial layer of the second end cap in an axialdirection of the second boss to form a substantially fluid tight sealtherebetween; and forming an outer shell around the main body, at leasta portion of the first boss, at least a portion of the second boss, thefirst interface, the second interface, and at least a portion of thefirst end cap and at least a portion of the second end cap, to securethe main body to the first end cap, wherein the inner surfaces of theinterfacial layers and the inner surface of the main body togetherdefine an interior cavity of the vessel for containing a pressurizedfluid, wherein the inner surface of the main body is a major surface ofthe interior cavity and the inner surfaces of the interfacial layers area minor surface of the interior cavity, wherein at least a portion ofeach of the first boss and the second boss is disposed between the outershell and the second surface of the interfacial layer in an axialdirection of the boss, and wherein the outer shell is in direct contactwith an outer surface of the first boss, an outer surface of the secondboss, the interfacial layer of the first end cap, and the interfaciallayer of the second end cap.
 17. The method of claim 16, furthercomprising forming the main body by a coextrusion blow film moldingprocess prior to the disposing step.
 18. The method of claim 16, furthercomprising forming the first end cap and the second cap by one of aninjection molding and a thermoforming process prior to the disposingstep.
 19. The method of claim 16, wherein forming an outer shell aroundthe main body and at least a portion of the first end cap and at least aportion of the second end cap comprises a filament winding and curingprocess.
 20. The method of claim 16, wherein the first boss includes asecond gasket disposed between and in direct contact with the firstcomponent of the first boss and the second component of the first bossin an axial direction of the first boss to form a substantiallyfluid-tight seal therebetween.